This invention pertains to a method for forming a chisel-type saw-chain cutter link, and more particularly, to a method for forming a substantially right-angle bend in such a link.
A chisel-type saw-chain cutter link is one which includes a substantially right-angle bend in the blank with the outside of the bend being defined by a sharp corner. Methods proprosed in the past for manufacturing such a link have not been entirely satisfactory. For example, casting a link with such a bend, followed by grinding of the bend's outside corner, is quite an expensive operation. Methods have been proposed essentially for bending a flat blank to produce the desired bend, but these have not been particularly successful. For example, where an attempt is made to produce, in a single bending operation, a bend of the finally desired angle, breakage is often a problem.
A general object of the present invention is to provide a unique cold-forming method for forming a link of the type described, in which relatively simple bending steps are used to produce the final desired bend, with the requisite degree of outside corner sharpness.
According to a preferred manner of practicing the invention, the proposed method includes the producing of an initial larger-than-desired-final-angle bend along a first bend line in the blank, then shifting the bend, so-to-speak, so as to shift the bend line in the blank toward a location spaced laterally from that of the first made bend, and more particularly toward the line along which the finally desired bend is to be located, and while so shifting the bend, decreasing its angle toward the desired final angle, and flowing material in the blank generally in the direction of bend-line shifting. In the specific way of practicing the method which is illustrated and described herein, four bending steps are utilized, each producing a bend in a blank along a different laterally spaced line in the blank, progressing from an initial bend line toward a final bend line. Following the making of the initial bend, the making of each subsequent bend results in flattening of the prior-made bend accompanied by flowing of material from the region of the prior-made bend toward the region of the next bend.
The proposed method, therefore, results in the flowing of material generally toward the region where the final bend is located, with such flowing both obviating the breakage problem which has been encountered in prior art methods, and forcing material to form a sharp outside corner defining the outside of the final bend.
Another feature of the invention is that the type of bending contemplated is usable to considerable advantage in connection with bending along the line of "grain" in a metal blank. This allows the simple production of cutter links from a continuous metal strip. It has been thought, heretofore, that successful bending operations to produce a link of the type outlined could be produced only in a "cross-grain" direction. Consistent breakage characterized prior art attempts to bend in the direction of the grain. The steps contemplated by the present invention readily allow bending in the direction of the grain, and have been found to produce cutter links with strength characteristics superior to those achieved with prior art cross-grain bent links.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.